Ultrasound imaging is currently widely used by the medical profession to view internal soft human tissue. It is used to examine internal organs and to locate and examine abnormal and diseased tissue such as malignant tumors. With the advent of so-called “Doppler” (color) ultrasound equipment, vascular imaging became possible, as this equipment is able to sense the slight frequency shifts in reflected ultrasonic emissions caused by the movement of blood and it solid constituents. This and other improvements in ultrasound technology have enhanced it usefulness in recent years.
The use of ultrasound imaging as the primary or preferred monitoring system during, for example, minimally invasive surgical procedures such as fine needle biopsies, has become more prevalent as the use of ultrasound have become more widespread. The health advantages to the patient over, for example X-ray imaging techniques, however, have been somewhat offset by the shortcoming that needles and other small instruments are virtually invisible to ultrasound imaging systems. The medical professional has a critical need to be able to accurately see and locate the position of surgical instruments or treatment options such as those utilized in brachytherapy relative to target tissue. Several patents that recognized these needs have been issued.
U.S. Pat. No. 4,249,539 to Vilkomerson et al. describes a system which includes an omnidirectional ultrasonic transducer located at a needle tip. The transducer can be used either as a receiver of signals from the imaging transducer or as both receiver and transmitter. This system achieves the objective of visibility but has the disadvantage that the ultrasound equipment electronics must be designed to interact with the transducer and that the transducer must be inserted into the body.
U.S. Pat. No. 5,095,910 to Powers describes a system that includes and inner solid element that reciprocates longitudinally at audio frequencies within a hollow member. The use of this motion to achieve visibility, inspired by an effect first noticed by ultrasound practitioners, is described. The invention requires that the member, which may be a hollow needle for aspiration, contain the reciprocating member to remain visible. The system, by design, displays the tip rather than the whole needle, thus denying the operator the ability to observe neither the angle of entry nor the proximity of the needle to vital tissue such as nerve tissue or arteries.
U.S. Pat. No. 5,329,927 to Gardineer et al. describes a color ultrasonic imaging system for visualizing the tip of an interventional medical device such as a biopsy needle in the body of a patient. The patent describes an apparatus and method for generating a periodic or oscillating mechanical motion in the form of flexural waves in the X, Y and Z axes in the needle. This results in the generation of a significant Doppler shift effect that enables the needle to be detected by a color ultrasonic imaging system. The needle is made to oscillate by a mechanical motion mechanism or VIBER coupled thereto. The needle is coupled and secured to the mechanism using a flexible clip-like element formed from any suitable metal or plastic material. The flexible clip-like element is designed to accommodate and secure needles of different gauges to the mechanical motion inducing mechanism. Problems, however, having to do with assured fixation or attachment of the needle to the mechanical motion mechanism arise due to the fixed diameter of the flexible clip-like element which works well only with a narrow range of needle gauges. Moreover, the mechanical motion mechanism is generally very expensive to manufacture.
U.S. Pat. No. 5,967,991 to Gardineer et al. describes a disposable, single-element piezoelectric vibrating device. The driving method taught by this patent includes a vibrating piezoelectric element that couples its energy into an elongated member by means of a coupling bracket. The frequency of the piezoelectric element excitation is then varied to match the natural resonance frequency of the biopsy needle so as to induce a maximum vibration at it tip. As the resonant frequency of the needle can vary according to the density and elasticity of it environment (surrounding tissue) this method can require frequent operator adjustment. The single element produces vibrations primarily in one plane, requiring the operator to rotate the needle at times to maintain its visibility. As a practical matter, the problem of tailoring the natural resonance frequencies of all biopsy needles of various lengths and gauges is difficult in mass production.
Finally, U.S. Pat. No. 6,053,871 to Cockburn et al. describes the generation and transmission of an oscillating motion of an air column to the tip of a needle so that the location of the tip is visible by a color Doppler U.S. scanner. The oscillating system is made of a loud speaker, an amplifier, a separate signal generator and tubing connecting the amplifier to the needle hub. The system suffers from such limitations as the relative inefficiency of the loud speaker with regard to the generating sufficient motion into various tissues, the need for a design that prevents tissue from entering the needle while allowing the signal to exit, and the presence of connecting tubes that may limit manipulation of the needle.
Thus, there remains a need for a practical and more versatile medical device with it own built-in high quality, low cost vibrating assembly to accomplish the objectives envisioned by Gardineer et al. in U.S. Pat. No. 5,967,991.